A Morphological study of the Intermediate Splanchnic Ganglion

Introduction: Intermediate ganglia are located outside the sympathetic trunk on the rami communicantes, splanchnic nerves, sympathetic branches or spinal nerves. Splanchnic ganglion of the greater splanchnic nerve was first described by Lobstein in 1823. These ganglia give off medial branches to the aortic coat, celiac plexus, superior mesenteric plexus, renal plexus or oesophageal plexuses. Splanchnic nerves with intermediate ganglia are neural structures with synaptic relay and not just conduction pathways. Aim: To study the incidence and structure of the intermediate ganglion in relation to thoracic splanchnic nerves and its connections in cadavers. Materials and Methods: Study design consisted of 50 cadavers of either sex, between 45 and 70 years of age, embalmed by conventional method for undergraduate Anatomy classes. After the removal of thoracic and abdominal viscera, the diaphragm was cut close to posterior abdominal wall and the parietal pleurae were carefully stripped off the posterior thoracic wall. Thoracic splanchnic nerves were defined and traced to the sympathetic trunk. Size, location, branches and microanatomy of the intermediate ganglion, if any, present on the thoracic splanchnic nerves were studied. Results: Intermediate splanchnic ganglia were observed macroscopically on the greater splanchnic nerve in 52% of the right and left sides of 50 cadavers examined. Bilateral presence of ganglia was seen in 13 cadavers. The trunk of the greater splanchnic nerve was thickened in 12 specimens where a macroscopic ganglion was not appreciated. Microanatomy of the intermediate ganglion, studied by haematoxylin and eosin stain, demonstrated a structure similar to that of sympathetic ganglion. Presence of macroscopic ganglion and nerve thickening was not observed in lesser or least splanchnic nerves. Conclusion: Present study demonstrates the location of the intermediate splanchnic ganglia and its medial branches which communicates with aortic plexus. Intermediate splanchnic ganglia connected to aortic plexuses could act as a residual pathway after sympathectomies. Thus, denervation of the medial branches may also be needed in future to have complete pain relief after sympathectomies.